Zoom lens and camera device

ABSTRACT

The zoom lens comprises five or more groups of lens pieces, namely, the foremost or first lens group of positive refractive power located the closest to an object, the succeeding second lens group of negative refractive power, the third lens group of positive refractive power, the fourth lens group of positive refractive power, and the fifth lens group all arranged in this order, and if any, the rearmost lens group(s) closer to the imaging plane than the fifth lens group. The zoom lens meets requirements as defined in the conditional expression regarding a combined magnification of the fifth lens group and, if any, the rearmost lens group(s) closer to the imaging plane than the fifth lens group while the zoom lens is taking a telephoto position.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a Continuation of application Ser. No.14/140,702, filed Dec. 26, 2013, which claims priority from JapaneseApplication No. 2012-286011 filed Dec. 27, 2012, both of which areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to zoom lenses, interchangeable lens unitsincorporating the zoom lenses, and camera devices used with the same.More particularly, the present invention relates to high variable powercompact zoom lenses suitable to camera optical systems for digitizedsignal input/output devices such as digital still cameras, digital videocameras, and the like, interchangeable lens units incorporating the highvariable power compact zoom lenses, and camera devices used with thesame.

BACKGROUND ART

Recently, camera devices, such as digital still cameras, incorporatingsolid-state image sensors have been popular. This tendency of the marketdemand has been followed by the performance improvement and downsizingof optical systems, and more compact camera systems have rapidly becomecommercially available. Optical systems in such camera systems are ofhigher-performance oriented and increasingly downsizing oriented designto meet the market demand for zoom lens optical systems with a shortenedentire length and a reduced diameter. Especially, it is highly desiredthat optical systems, such as tele-photographing zoom lenses, having anincreased focal length should be of more enhanced performance andreduced dimensions.

One prior art tele-photographing zoom lens, which satisfies the desiredperformance and dimensions to such an extent that the zoom lens has itsoptical system extended up to 318.283-mm entire length for attaining490-mm maximum focal length in one embodiment, comprises the foremost orfirst lens group L1 of positive refractive power located the closest toan object, the succeeding or second lens group L2 of negative refractivepower, the third lens group L3 of positive refractive power, the fourthlens group L4 of positive refractive power, the fifth lens groupincluding an aperture stop, and the rearmost or sixth lens group L6 ofnegative refractive power arranged in this precise order, and the zoomlens has its first, fourth, fifth and sixth lens groups L1, L4, L5 andL6 moved toward the object for varying magnification from the wide-angleposition to the telephoto position and has its third lens group L3 movedtoward the imaging plane for compensating for field displacementresulting from the varied magnification (e.g., see Patent Document 1listed below).

Such a prior art zoom lens meets the requirements as defined in thefollowing conditional expression:

With a lens piece the closest to the imaging plane in the lens group L1being shaped in convex lens,0.45≤f1/ft≤0.58

where f1 is a focal length of the first lens group L1, and ft is a focallength of the optical system as a whole at a telephoto position,0.25≤|f2|/ft≤0.35

where f2 is a focal length of the second lens group L2,0.30≤f3/ft≤0.35

where f3 is a focal length of the third lens group L3,0.12≤|f6|/ft≤0.18

where f6 is a focal length of the sixth lens group L6, and1.2≤m1/m6≤2.0

where m1 is a displacement of the first lens group L1 resulting from thevariation in magnification, and m6 is a displacement of the sixth lensgroup L6 resulting from the variation in magnification.

LIST OF DOCUMENTS OF THE RELATED ART Patent Document 1

Official Gazette of JP-A-2003-344768

The prior art tele-photographing zoom lens mentioned above is stillunsatisfactory in that the rearmost lens group exhibits an insufficientmagnification at the telephoto end while the zoom lens as a whole is yetundesirably long when taking a telephoto position. Another disadvantageis an undesirably great displacement of the first lens group.

Allowing for the aforementioned disadvantages in the prior art, thepresent invention is directed to providing an improved zoom lens thatattains high-performance imaging suitable to attachment lenses and/orcamera devices incorporating solid-state image sensors, such as digitalstill cameras, digital video cameras, and the like, of which pixels aremuch more minute than those of photographing film, and providing animproved camera device used with such a zoom lens.

The present invention is also directed to providing an improved zoomlens in which, when the zoom lens takes a telephoto posture, therearmost lens group(s) exhibits a greater magnification, namely, agreater rate of an angle (in radians) of beams incident upon therearmost lens group(s) to an angle (in radians) of exiting beams fromthe same so as to have a reduced extension of an optical system as awhole of the zoom lens at the telephoto end and attain a reduceddisplacement of the first lens group, and to providing a camera deviceused with such a zoom lens.

SUMMARY OF THE INVENTION

A zoom lens comprises five or more groups of lens pieces, namely, theforemost or first lens group of positive refractive power located theclosest to an object, the succeeding second lens group of negativerefractive power, the third lens group of positive refractive power, thefourth lens group of positive refractive power, and the fifth lens groupall arranged in this order, and if any, the rearmost lens group(s)closer to the imaging plane than the fifth lens group; and the zoom lenstaking a telephoto position meets requirements as defined in thefollowing conditional expression:3.1≤βbt≤4.0  (1)

where βbt is a combined lateral magnification of the fifth lens groupand, if any, the rearmost lens group(s) closer to the imaging plane thanthe fifth lens group while the zoom lens is taking a telephoto position.

A camera device comprises solid-state image sensors disposed on orbehind the imaging plane of a zoom lens for converting an optical imagecreated by the zoom lens into electrical signals, the zoom lenscomprising five or more groups of lens pieces, namely, the foremost orfirst lens group of positive refractive power located the closest to anobject, the succeeding second lens group of negative refractive power,the third lens group of positive refractive power, the fourth lens groupof positive refractive power, and the fifth lens group all arranged inthis order, and if any, the rearmost lens group(s) closer to the imagingplane than the fifth lens group; the zoom lens in a telephoto positionmeeting requirements as defined in the following conditional expression(1):3.1≤βbt≤4.0  (1)

where βbt is a combined lateral magnification of the fifth lens groupand, if any, the rearmost lens group(s) closer to the imaging plane thanthe fifth lens group while the zoom lens takes a telephoto position.

In accordance with the present invention, the zoom lens, comprising atleast five lens groups, namely, the first lens group of positiverefractive power, the second lens group of negative refractive power,the third lens group of positive refractive power, the fourth lens groupof positive refractive power, and the fifth lens group, is capable ofvarying five or more dimensional components or distances between thelens groups adjacent to each other during varying its magnification soas to obtain an increased options to compensate for aberrations.

Also, in accordance with the present invention, the zoom lens attainshigh-performance imaging suitable to the interchangeable lenses and/orcamera device incorporating solid-state image sensors, such as digitalstill cameras, digital video cameras, and the like, of which pixels aremuch more minute than those of photographing film, and the camera deviceis suitably used with such a zoom lens.

Moreover, in accordance with the present invention, when the zoom lenstakes a telephoto position, the rearmost lens group(s) exhibits agreater magnification, namely, a greater rate of an angle (in radians)of beams incident upon the rearmost lens group(s) to an angle (inradians) of exiting beams from the same so as to have a reducedextension of an optical system as a whole of the zoom lens at thetelephoto end and attain a reduced displacement of the first lens group,and the camera device is suitably used with such a zoom lens.

In a first aspect of the present invention, the zoom lens meetsrequirements as defined in the following conditional expression (2):0.5≤f1/√{square root over ((fw×fT))}≤1.3  (2)

where fw is a focal length of the zoom lens taking a wide-angleposition, fT is a focal length of the zoom lens taking a telephotoposition, and f1 is a focal length of the first lens group.

Preferably, the zoom lens in the first aspect of the invention meetsrequirements as defined in the following conditional expression (2′):0.6≤f1/√{square root over ((fw×fT))}≤1.2  (2′)

More preferably, the zoom lens in the first aspect of the inventionmeets requirements as defined in the following conditional expression(2″):0.7≤f1/√{square root over ((fw×fT))}≤1.1  (2″)

In the zoom lens in the first aspect of the present invention, the fifthlens group and/or, if any, the rearmost lens group(s) behind the fifthlens group may be of negative refractive power.

The zoom lens in the first aspect of the present invention may have thesecond lens group held in a fixed position while the zoom lens as awhole is being displaced from the wide-angle position to the telephotoposition to vary magnification.

In the zoom lens in the first aspect of the present invention, the firstlens group may comprise one or more lens pieces that meet a requirementas defined in the following conditional expression (3):0.018≤ΔPgF  (3)

where PgF is the partial dispersion for glass for the respectivewavelengths 435.8 nm, 486.1 nm, and 656.3 nm of spectral lines g, F, andC, given by the equationPgF=(ng−nF)/(nF−nC),

where ng, nF, and nC are the refractive indices for the respectivewavelengths 435.8 nm, and 486.1 nm, and 656.3 nm of spectral lines g, F,and C, and

ΔPgF is a deviation from a straight line defined by a first point havingas its x, y coordinates the Abbe constant on the d-line νd=60.49 and thepartial dispersion PgF=0.5398 for a glass type C7 and a second pointhaving as its x, y coordinates the Abbe constant on the d-line νd=36.30and the partial dispersion PgF=0.5393 for a glass type F2, where theAbbe constant on the d-line νd is given by the following equation:νd=(nd−1)/(nF−nC),

where nd is the refractive index for the wavelength 589.6 nm of spectralline d.

The zoom lens in the first aspect of the present invention meetsrequirements as defined in the following conditional expression (4):0.60≤Lt/fT≤0.75  (4)

where Lt is an entire length of the optical system of the zoom lenstaking a telephoto position, and fT is a focal length of the same of thezoom lens at the telephoto end.

In the zoom lens in the first aspect of the present invention, the fifthlens group and/or, if any, the rearmost lens group(s) behind the fifthlens group may be displaced during varying magnification.

The zoom lens in the first aspect of the present invention may comprisean aperture stop closer to the imaging plane than the second lens group,and all or part of the lens groups closer to the imaging plane than theaperture stop are displaced along the optical axis to shift a focalpoint from the point at infinity to an object at the near point.

The zoom lens in the first aspect of the invention may have one or moreof the lens groups closer to the imaging plane than the fifth lens groupdisplaced toward the object during shifting from the wide-angle positionto the telephoto position to vary magnification.

The combined lateral magnification of one or more of the lens groupscloser to the imaging plane than the fifth lens group can be increasedby displacing it or them during shifting from the wide-angle position tothe telephoto end to vary magnification.

When an actual value of @bt is smaller than the lower limit defined inthe conditional expression (1), the fifth lens group and, if any, therearmost lens group(s) behind the fifth lens group attain a reducedeffect of raising the magnification, and resultantly, the zoom lens hasto have the increased entire length at the telephoto end. Accordingly,this brings about an increase in a displacement of the first lens groupfor varying magnification, which necessitates a more complicated cammechanism for displacing the first lens group, and resultantly, hindersdownsizing the lens barrel as a whole.

When the actual value of @bt exceeds the upper limit defined in theconditional expression (1), the fifth lens group and, if any, therearmost lens group(s) behind the fifth lens group attain an excessiveeffect of raising the magnification, which results in a smaller numberof the lens pieces encountering a difficulty in compensating foraberrations.

The zoom lens satisfying the conditions defined in the conditionalexpression (1) can have the reduced entire length at the telephoto end,which is useful to reduce the displacement of the first lens group forvarying magnification, and can permit the reduced number of the lenspieces to satisfactorily compensate for aberrations. Thus, fulfillingthe conditions in the conditional expression (1) enables the resultantzoom lens to simultaneously attain downsizing the lens barrel as a wholeand improving its performance.

When an actual value f1/√(fw·fT) is smaller than the lower limit definedin the conditional expression (2) and the first lens group has itspositive refractive power intensified, the zoom lens develops chromaticaberration more greatly at the telephoto end to such an undesired extentthat it is hard to compensate for the chromatic aberration. When theactual value f1/√(fw·fT) exceeds the upper limit defined in theconditional expression (2) and the first lens group has its positiverefractive power weakened, a flux of beams incident upon the second lensgroup unsatisfactorily converges, which results in the second lens groupbeing larger in dimensions and necessitate a greater displacement of thefirst lens group to such an undesired extent that it is unavoidable forthe lens barrel as a whole to be larger in dimensions.

Fulfilling the condition of abnormal dispersion of the lens pieces inthe first lens group as defined in the conditional expression (3)enables the zoom lens at the telephoto end to satisfactorily compensatefor longitudinal chromatic aberration.

Fulfilling the conditions of the entire length of the optical system ofthe zoom lens at the telephoto end as defined in the conditionalexpression (4) makes it possible to attain a telephotographing zoom lensthat, especially taking a telephoto position, has its optical systemconsiderably reduced in entire length. When an actual value of Lt/fT issmaller than the lower limit defined in the conditional expression (4),the zoom lens at the telephoto end has its optical system excessivelyreduced in entire length, and the zoom lens, especially taking awide-angle position, fails to ensure the desired optical performance.

When the actual value of Lt/fT exceeds the upper limit as defined in theconditional expression (4), the resultant telephotographing zoom lens atthe telephoto end has its optical system increased in entire length,which hinders downsizing the lens barrel as a whole.

Meeting the requirements defined in the conditional expression (4)enables the resultant optical system to implement an enhanced imagingperformance and the lens barrel as a whole to be downsized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view showing a lens arrangement in afirst embodiment of a zoom lens according to the present invention whenthe zoom lens is taking a wide-angle position,

FIG. 2 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the first embodiment of the zoom lenswhen the zoom lens taking a wide-angle position is in focus on the pointat infinity, the graphs of spherical aberration showing a rate of a stopsetting F-number to the full diaphragm stop setting F-number on thevertical axis and a degree of defocusing on the horizontal axis for thed-line (wavelength 587.6 nm) expressed by solid line, the c-line(wavelength 656.3 nm) by broken line, and the g-line (wavelength 435.8nm) by alternate long and short dash line, the graphs of astigmatismshowing an image height on the vertical axis and a degree of defocusingon the horizontal axis for a sagittal imaging plane expressed by solidline and a meridional imaging plane by broken line, and the graphs ofdistortion aberration show an image height on the vertical axis and adegree of distortion in percentage,

FIG. 3 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the first embodiment of the zoom lenswhen the zoom lens taking an intermediate zooming range position is infocus on the point at infinity,

FIG. 4 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the first embodiment of the zoom lenswhen the zoom lens taking a telephoto position is in focus on the pointat infinity,

FIG. 5 is a vertical sectional view showing a lens arrangement in asecond embodiment of the zoom lens according to the present inventionwhen the zoom lens is taking a wide-angle position,

FIG. 6 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the second embodiment of the zoomlens when the zoom lens taking a wide-angle position is in focus on thepoint at infinity,

FIG. 7 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the second embodiment of the zoomlens when the zoom lens taking an intermediate zooming range position isin focus on the point at infinity,

FIG. 8 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the second embodiment of the zoomlens when the zoom lens taking a telephoto position is in focus on thepoint at infinity,

FIG. 9 is a vertical sectional view showing a third embodiment of thezoom lens according to the present invention when the zoom lens istaking a wide-angle position,

FIG. 10 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the third embodiment of the zoom lenswhen the zoom lens taking a wide-angle position is in focus on the pointat infinity,

FIG. 11 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the third embodiment of the zoom lenswhen the zoom lens taking an intermediate zooming range position is infocus on the point at infinity,

FIG. 12 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the third embodiment of the zoom lenswhen the zoom lens taking a telephoto position is in focus on the pointat infinity,

FIG. 13 is a vertical sectional view showing a fourth embodiment of thezoom lens according to the present invention when the zoom lens istaking a wide-angle position,

FIG. 14 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fourth embodiment of the zoomlens when the zoom lens taking a wide-angle position is in focus on thepoint at infinity,

FIG. 15 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fourth embodiment of the zoomlens when the zoom lens taking an intermediate zooming range position isin focus on the point at infinity,

FIG. 16 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fourth embodiment of the zoomlens when the zoom lens taking a telephoto position is in focus on thepoint at infinity,

FIG. 17 is a vertical sectional view showing a fifth embodiment of thezoom lens according to the present invention when the zoom lens istaking a wide-angle position,

FIG. 18 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fifth embodiment of the zoom lenswhen the zoom lens taking a wide-angle position is in focus on the pointat infinity,

FIG. 19 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fifth embodiment of the zoom lenswhen the zoom lens taking an intermediate zooming range position is infocus on the point at infinity, and

FIG. 20 depicts graphs of spherical aberration, astigmatism, anddistortion aberration developed in the fifth embodiment of the zoom lenswhen the zoom lens taking a telephoto position is in focus on the pointat infinity.

BEST MODE OF THE INVENTION Embodiment 1

FIG. 1 is a vertical sectional view showing a lens arrangement of afirst embodiment of a zoom lens according to the present invention. Thefirst embodiment of the zoom lens comprises the foremost or first lensgroup G1 of positive refractive power located the closest to an object,the succeeding second lens group G2 of negative refractive power, thethird lens group G3 of positive refractive power, the fourth lens groupG4 of positive refractive power, the fifth lens group G5 of negativerefractive power, and the rearmost or sixth lens group G6 of negativerefractive power arranged in this order.

The first lens group G1 comprises a duplet of a meniscus lens piece L1of negative refractive power with its convex surface oriented to theobject and a lens piece L2 of positive refractive power cemented withthe meniscus lens piece L1, and a lens piece L3 of positive refractivepower, all the lens pieces being arranged in this order from the closestto the object in the foremost position to the farthest in the rearmostposition.

The second lens group G2 comprises a duplet of a lens piece L4 ofnegative refractive power with its concave surface oriented toward theobject and a meniscus lens piece L5 of positive refractive powercemented with the lens piece L4, and a meniscus lens piece L6 ofnegative refractive power with its concave surface oriented toward theobject.

The third lens group G3 comprises a biconvex lens piece L7, a biconvexlens piece L8, a duplet of a lens piece L9 of positive refractive powerwith its convex surface oriented toward the object and a lens piece L10of negative refractive power cemented with the lens piece L9, andanother duplet of a biconcave lens piece L11 and a meniscus lens pieceL12 of positive refractive power with its convex surface oriented towardthe object, all the lens pieces arranged in this order from the closestto the object in the foremost position to the farthest in the rearmostposition.

The fourth lens group G4 comprises a biconvex lens piece L13, and aduplet of a lens piece L14 of positive refractive power with its convexsurface oriented toward the object and a lens piece L15 of positiverefractive power cemented with the lens piece L14, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest from the object in the rearmostposition.

The fifth lens group G5 comprises a duplet of a biconvex lens piece L16positioned closer to the object and a biconcave lens piece L17 cementedwith the biconvex lens piece L16.

The sixth lens group G6 comprises a meniscus lens piece L18 of negativerefractive power with its concave surface oriented toward the object.

During varying magnification from the wide-angle and to the telephotoend, the first embodiment of the zoom lens has its first lens groupmoved toward the object, its second lens group held in a fixed position,its third lens group moved on a trajectory that draws an arc toward theimaging plane relative to the second lens group, its fourth lens groupmoved on a trajectory that draws an arc toward the imaging planerelative to the third lens group, its fifth lens group moved toward theobject, and its sixth lens group moved in the same manner as the fourthlens group.

Focusing on an object at the near point is carried out by moving thefifth lens group toward the imaging plane. For that purpose, the dupletof the lens pieces L11 and L12 cemented together is moved in verticaldirections normal to the optical axis so as to correct fuzziness of animage during photographing.

Optical data of the lens pieces in the first embodiment of the zoom lensare provided in Table 1. Surface number NS designates the n-th lenssurface of the optical system where all the component lens pieces arearranged in order on the closest-to-the-object-first basis, R is aradius of curvature of the n-th lens surface, D is a distance along theoptical axis between a pair of the adjacent lens surfaces, Nd is arefractive index for the d-line (wavelength λ=587.6 nm), and νd is anAbbe number for the d-line (wavelength λ=587.6 nm).

TABLE 1 NS R D Nd vd ΔPgF  1 486.4782 1.4500 1.83400 37.34  2 83.33990.0100 1.56732 42.84  3 83.3399 5.5100 1.49700 81.61 0.0375  4 −172.82140.1500  5 63.2093 5.2914 1.48749 70.44  6 −895.6302 D(6)   7 0.00001.8876  8 −96.2544 0.7500 1.76524 50.37  9 18.4045 0.0100 1.56732 42.8410 18.4045 3.0631 1.80518 25.46 11 70.9807 2.5194 12 −41.5515 0.70001.80420 46.50 13 −10114.4818 D(13) 14 39.2470 4.1119 1.49700 81.61 15−41.3613 0.1000 16 40.1380 2.6375 1.48749 70.44 17 −1692.6300 0.1000 1843.0535 3.8276 1.48749 70.44 19 −29.6342 0.0100 1.56732 42.84 20−29.6342 0.7000 1.90739 33.25 21 119.5406 6.7000 22 −1390.5046 0.60001.77791 44.07 23 18.4637 0.0100 1.56732 42.84 24 18.4637 2.3536 1.9036631.31 25 48.8224 2.3000 26 STOP 0.0000 D(26) 27 52.7369 2.8298 1.5673242.84 28 −27.8361 0.1000 29 26.5392 3.2246 1.54356 46.62 30 −23.13960.0100 1.56732 42.84 31 −23.1396 0.6000 1.90366 31.31 32 104.0723 D(32)33 54.2263 1.4342 1.80518 25.46 34 −61.6536 0.0100 1.56732 42.84 35−61.6536 0.5600 1.74161 49.80 36 16.9498 D(36) 37 −24.4610 0.93001.48749 70.44 38 −87.3035 0.0000 39 0.0000 D(39) 40 0.0000 2.80001.51680 64.20 41 0.0000 1.0000

Distances between the adjacent lens surfaces in several pairs in thefirst embodiment of the zoom lens are given in Table 2 below as well asvaried values of the focal distance f, the F-number Fno, and the fieldangle ω for each of the zooming settings at the wide-angle position(f=68.7634), at the intermediate zooming range (f=149.5669), and at thetelephoto position (f=291.2580), respectively.

TABLE 2 f 68.7634 149.5669 291.2580 Fno 4.62776 5.18280 6.80830 ω 6.80043.13810 1.61270 D(6) 18.4552 49.5086 57.3552 D(13) 24.5140 18.29701.5000 D(26) 4.3452 4.2773 7.7592 D(32) 5.4806 1.4000 2.7630 D(36)11.0774 15.1581 13.7950 D(39) 19.7269 26.0118 39.3269

Distances between the adjacent lens surfaces in several pairs in thefirst embodiment of the zoom lens during focusing on an object at thenear point for zooming settings at the wide-angle position (f=68.7634),at the intermediate zooming range (f=149.5669), and at the telephotoposition (f=291.2580), respectively, are given in Table 3 below as wellas varied values of the focal length f upon focusing on an object atinfinite distance away and the distance D(0) from the front surface ofthe first lens piece to the object.

TABLE 3 f 68.7634 149.5669 291.2580 D(0) 1058.11 1027.06 1019.21 D(32)6.6285 4.8033 12.0080 D(36) 9.9260 11.7548 4.5501

Embodiment 2

FIG. 5 is a vertical sectional view showing a lens arrangement of asecond embodiment of the zoom lens according to the present invention.The second embodiment of the zoom lens comprises the foremost or firstlens group G1 of positive refractive power located the closest to anobject, the succeeding second lens group G2 of negative refractivepower, the third lens group G3 of positive refractive power, the fourthlens group G4 of positive refractive power, and the fifth lens group G5of negative refractive power, all the lens groups being arranged in thisorder.

The first lens group G1 comprises a duplet of a meniscus lens piece L1of negative refractive power with its convex surface oriented to theobject and a lens piece L2 of positive refractive power cemented withthe meniscus lens piece L1, and a meniscus lens piece L3 of positiverefractive power with its convex surface oriented to the object, all thelens pieces being arranged in this order from the closest to the objectin the foremost position to the farthest in the rearmost position.

The second lens group G2 comprises a duplet of a lens piece L4 ofpositive refractive power and a lens piece L5 of negative refractivepower cemented with the lens piece L4, another duplet of a lens piece L6of positive refractive power with its convex surface oriented toward theobject and a lens piece L7 of negative refractive power cemented withthe lens piece L6, and a meniscus lens piece L8 of negative refractivepower with its concave surface oriented to the object, all the lenspieces being arranged in this order from the closest to the object inthe foremost position to the farthest in the rearmost position.

The third lens group G3 comprises a biconvex lens piece L9, a biconvexlens piece L10, a duplet of a lens piece L11 of positive refractivepower with its convex surface oriented to the object and a lens pieceL12 of negative refractive power cemented with the lens piece L11, andanother duplet of a biconcave lens piece L13 and a meniscus lens pieceL14 of positive refractive power with its convex surface oriented to theobject, and cemented with the biconcave lens piece L13, all the lenspieces being arranged in this order from the closest to the object inthe foremost position to the farthest in the rearmost position.

The fourth lens group G4 comprises a biconvex lens piece L15, and aduplet of a lens piece L16 of positive refractive power with its convexsurface oriented toward the object and a lens piece L17 of negativerefractive power cemented with the lens piece L16, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest from the object in the rearmostposition.

The fifth lens group G5 comprises a lens piece L18 of negativerefractive power with its convex surface oriented toward the object, anda duplet of a biconcave lens piece L19 and a lens piece L20 of positiverefractive power cemented with the lens piece L19, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest in the rearmost position.

During varying magnification from the wide-angle and to the telephotoend, the second embodiment of the zoom lens has its first lens groupmoved toward the object, its second lens group held in a fixed position,its third lens group moved on a trajectory that draws an arc toward theimaging plane relative to the second lens group, its fourth lens groupmoved on a trajectory that draws an arc toward the imaging planerelative to the third lens group, and its fifth lens group moved towardthe object.

For focusing on an object at the near point, the fourth lens group ismoved toward the imaging plane. The duplet of the cemented lens piecesL13 and L14 are moved in directions normal to the optical axis so as tocorrect fuzziness of an image during photographing.

Optical data of the second embodiment of the zoom lens are provided inTable 4.

TABLE 4 NS R D Nd vd ΔPgF  1 507.2915 3.0000 1.83400 37.34  2 170.56510.0200 1.56732 42.84  3 170.5651 10.0500 1.49700 81.61 0.0375  4−546.9417 0.3000  5 140.0409 9.1000 1.49700 81.61 0.0375  6 6747.4128D(6)  7 −462.7175 4.4000 1.80518 25.46  8 −59.7377 0.0100 1.56732 42.84 9 −59.7377 1.6000 1.75540 47.52 10 89.4635 1.7000 11 84.1934 4.03221.80518 25.46 12 −143.0460 0.0100 1.56732 42.84 13 −143.0460 1.40001.83481 42.72 14 103.1048 4.3467 15 −72.3495 1.5000 1.90366 31.31 16−959.3316 D(16) 17 96.4840 4.8156 1.49700 81.61 18 −93.3616 0.2000 19136.2135 3.8473 1.48749 70.44 20 −135.3488 0.2000 21 74.9337 5.35361.48749 70.44 22 −69.9732 0.0100 1.56732 42.84 23 −69.9732 1.50001.90366 31.31 24 −1625.6271 12.0000 25 −276.9348 1.2000 1.80393 37.39 2624.9138 0.0100 1.56732 42.84 27 24.9138 4.7931 1.83950 29.48 28 112.42094.5000 29 STOP 0.0000 D(29) 30 82.8644 4.6000 1.50601 60.25 31 −68.51460.2000 32 38.3468 5.4000 1.50163 62.32 33 −58.6905 0.0100 1.56732 42.8434 −58.6905 3.3708 1.90366 31.31 35 1283.2003 0.0000 36 0.0000 D(36) 37101.8564 1.3000 1.83481 42.72 38 24.0855 5.7488 39 −73.4446 1.35041.48749 70.44 40 24.7023 0.0100 1.56732 42.84 41 24.7023 5.6000 1.6688531.91 42 −3665.3014 D(42) 43 0.0000 2.0000 1.51680 64.20 44 0.00001.0000

Distances between the adjacent lens surfaces in several pairs in thesecond embodiment of the zoom lens are given in Table 5 below as well asvaried values of the focal distance f, the F-number Fno, and the fieldangle ω for each of the photographing positions at the wide-angleposition (f=151.9125), at the intermediate zooming range (f=300.56), andat the telephoto position (f=582.2009), respectively.

TABLE 5 f 151.9125 300.5600 582.2009 Fno 4.94595 5.91814 6.77715 ω7.9237 4.01640 2.07480 D(6) 64.0000 111.8284 141.2200 D(16) 34.616523.4740 2.0400 D(29) 28.9568 16.6652 23.1985 D(36) 9.6584 5.9504 3.1420D(42) 51.0000 78.1421 95.8512

Distances between the adjacent lens surfaces in several pairs in thesecond embodiment of the zoom lens during focusing on an object at thenear point for zooming settings at the wide-angle position (f=151.9125),at the intermediate zooming range (f=300.56), and at the telephotoposition (f=582.2009), respectively, are given in Table 6 below as wellas varied values of the focal length f upon focusing on an object atinfinite distance away and the distance D(0) from the front surface ofthe first lens piece to the object.

TABLE 6 f 151.9125 300.5600 582.2009 D(0) 2401.28 2353.45 2324.06 D(29)27.6147 13.4871 14.3841 D(36) 11.0005 9.1285 11.9565

Embodiment 3

FIG. 9 is a vertical sectional view showing a lens arrangement of athird embodiment of the zoom lens according to the present invention.The third embodiment of the zoom lens comprises the foremost or firstlens group G1 of positive refractive power located the closest to anobject, the succeeding second lens group G2 of negative refractivepower, the third lens group G3 of positive refractive power, the fourthlens group G4 of positive refractive power, and the fifth lens group G5of negative refractive power, all the lens groups being arranged in thisorder.

The first lens group G1 comprises a duplet of a meniscus lens piece L1of negative refractive power with its convex surface oriented to theobject and a lens piece L2 of positive refractive power cemented withthe meniscus lens piece L1, and a lens piece L3 of positive refractivepower, all the lens pieces being arranged in this order from the closestto the object in the foremost position to the farthest in the rearmostposition.

The second lens group G2 comprises a duplet of a lens piece L4 ofpositive refractive power with its convex surface oriented toward theobject and a lens piece L5 of negative refractive power cemented withthe lens piece L4, another duplet of a meniscus lens piece L6 ofnegative refractive power with its convex surface oriented toward theobject and a lens piece L7 of positive refractive power cemented withthe lens piece L6, and a meniscus lens piece L8 of negative refractivepower with its concave surface oriented to the object.

The third lens group G3 comprises a biconvex lens piece L9, a biconvexlens piece L10, a duplet of a lens piece L11 of positive refractivepower with its convex surface oriented to the object and a lens pieceL12 of negative refractive power cemented with the lens piece L11, andanother duplet of a biconcave lens piece L13 and a meniscus lens pieceL14 of positive refractive power with its convex surface oriented to theobject, and cemented with the biconcave lens piece L13, all the lenspieces being arranged in this order from the closest to the object inthe foremost position to the farthest in the rearmost position.

The fourth lens group G4 comprises a biconvex lens piece L15, and aduplet of a lens piece L16 of positive refractive power with its convexsurface oriented toward the object and a lens piece L17 of negativerefractive power cemented with the lens piece L16, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest from the object in the rearmostposition.

The fifth lens group G5 comprises a lens piece L18 of negativerefractive power with its convex surface oriented toward the object, anda duplet of a biconcave lens piece L19 and a meniscus lens piece L20 ofpositive refractive power with its convex surface oriented to theobject, and cemented with the lens piece L19, all the lens pieces beingarranged in this order from the closest to the object in the foremostposition to the farthest in the rearmost position.

During varying magnification from the wide-angle and to the telephotoend, the third embodiment of the zoom lens has its first lens groupmoved toward the object, its second lens group held in a fixed position,its third lens group moved on a trajectory that draws an arc toward theimaging plane relative to the second lens group, its fourth lens groupmoved on a trajectory that draws an arc toward the imaging planerelative to the third lens group, and its fifth lens group moved towardthe object.

For focusing on an object at the near point, the fourth lens group ismoved toward the object. The duplet of the cemented lens pieces L13 andL14 are moved in directions normal to the optical axis so as to correctfuzziness of an image during photographing.

Optical data of the third embodiment of the zoom lens are provided inTable 7.

TABLE 7 NS R D Nd vd ΔPgF  1 297.9129 2.8300 1.83400 37.34  2 135.03840.0200 1.56732 42.84  3 135.0384 9.3000 1.49700 81.61 0.0375  4−4966.1736 0.3000  5 146.0473 8.5000 1.49700 81.61 0.0375  6 −1305.5193D(6)  7 213.6104 4.2002 1.80518 25.46  8 −62.5956 0.0100 1.56732 42.84 9 −62.5956 1.5700 1.74645 49.97 10 144.9586 3.2900 11 612.2359 1.45001.83404 40.21 12 48.5752 0.0100 1.56732 42.84 13 48.5752 3.2100 1.8051825.46 14 152.1415 2.4500 15 −71.1073 1.4200 1.90366 31.31 16 2627.1686D(16) 17 97.4108 3.9312 1.49700 81.61 18 −83.4307 0.2000 19 126.70043.1209 1.48749 70.44 20 −143.7416 0.2000 21 69.4530 4.8712 1.48749 70.4422 −68.6082 0.0100 1.56732 42.84 23 −68.6082 1.4200 1.90366 31.31 24−2644.7437 12.0500 25 −271.3050 1.2500 1.82533 40.81 26 28.0112 0.01001.56732 42.84 27 28.0112 3.9500 1.89851 30.99 28 101.7617 4.4401 29 STOP0.0000 D(29) 30 89.3134 3.7900 1.52994 52.35 31 −63.6313 0.2000 3236.8157 5.1142 1.50170 69.40 33 −56.3810 0.0100 1.56732 42.84 34−56.3810 1.3200 1.90366 31.31 35 1002.5920 0.0000 36 0.0000 D(36) 37101.3957 1.2500 1.81828 43.28 38 23.0588 5.9200 39 −51.4450 1.40001.48749 70.44 40 26.1939 0.0100 1.56732 42.84 41 26.1939 5.4332 1.7257934.70 42 −206.0292 D(42) 43 0.0000 2.0000 1.51680 64.20 44 0.0000 1.0000

Distances between the adjacent lens surfaces in several pairs in thethird embodiment of the zoom lens are given in Table 8 below as well asvaried values of the focal distance f, the F-number Fno, and the fieldangle ω for each of the photographing positions at the wide-angleposition (f=153.8209), at the intermediate zooming range (f=286.8109),and at the telephoto position (f=485.2042), respectively.

TABLE 8 f 153.8209 286.8109 485.2042 Fno 4.95462 5.80954 6.48931 ω8.0054 4.31340 2.55290 D(6) 64.9509 105.7871 129.7209 D(16) 29.934617.8473 2.2000 D(29) 27.7446 20.6475 22.7820 D(36) 9.7788 6.8423 4.4105D(42) 51.3300 73.4510 89.3956

Distances between the adjacent lens surfaces in several pairs in thethird embodiment of the zoom lens during focusing on an object at thenear point for zooming settings at the wide-angle position (f=153.8209),at the intermediate zooming range (f=286.8109), and at the telephotoposition (f=485.2042), respectively, are given in Table 9 below as wellas varied values of the focal length f upon focusing on an object atinfinite distance away and the distance D(0) from the front surface ofthe first lens piece to the object.

TABLE 9 f 153.8209 286.8109 485.2042 D(0) 2014.80 1973.96 1950.03 D(29)26.0200 16.6583 13.9700 D(36) 11.5034 10.8315 13.2225

Embodiment 4

FIG. 13 is a vertical sectional view showing a lens arrangement of afourth embodiment of the zoom lens according to the present invention.The fourth embodiment of the zoom lens comprises the foremost or firstlens group G1 of positive refractive power located the closest to anobject, the succeeding second lens group G2 of negative refractivepower, the third lens group G3 of positive refractive power, the fourthlens group G4 of positive refractive power, and the fifth lens group G5of negative refractive power, all the lens groups being arranged in thisorder.

The first lens group G1 comprises a duplet of a meniscus lens piece L1of negative refractive power with its convex surface oriented to theobject and a lens piece L2 of positive refractive power cemented withthe meniscus lens piece L1, and a lens piece L3 of positive refractivepower, all the lens pieces being arranged in this order from the closestto the object in the foremost position to the farthest in the rearmostposition.

The second lens group G2 comprises a duplet of a lens piece L4 ofpositive refractive power with its convex surface oriented toward theobject and a lens piece L5 of negative refractive power cemented withthe lens piece L4, another duplet of a meniscus lens piece L6 ofnegative refractive power with its convex surface oriented toward theobject and a lens piece L7 of positive refractive power cemented withthe lens piece L6, and a meniscus lens piece L8 of negative refractivepower with its concave surface oriented to the object.

The third lens group G3 comprises a biconvex lens piece L9, a biconvexlens piece L10, a duplet of a lens piece L11 of positive refractivepower with its convex surface oriented to the object and a lens pieceL12 of negative refractive power cemented with the lens piece L11, andanother duplet of a biconcave lens piece L13 and a meniscus lens pieceL14 of positive refractive power with its convex surface oriented to theobject, and cemented with the biconcave lens piece L13, all the lenspieces being arranged in this order from the closest to the object inthe foremost position to the farthest in the rearmost position.

The fourth lens group G4 comprises a biconvex lens piece L15, and aduplet of a lens piece L16 of positive refractive power with its convexsurface oriented toward the object and a lens piece L17 of negativerefractive power cemented with the lens piece L16, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest from the object in the rearmostposition.

The fifth lens group G5 comprises a lens piece L18 of negativerefractive power with its convex surface oriented toward the object, anda duplet of a biconcave lens piece L19 and a meniscus lens piece L20 ofpositive refractive power with its convex surface oriented to theobject, and cemented with the lens piece L19, all the lens pieces beingarranged in this order on the basis of the foremost first.

During shifting from the wide-angle position to the telephoto positionto vary magnification, the fourth embodiment of the zoom lens has itsfirst lens group moved toward the object, its second lens group held ina fixed position, its third lens group moved on a trajectory that drawsan arc toward the imaging plane relative to the second lens group, itsfourth lens group moved on a trajectory that draws an arc toward theimaging plane relative to the third lens group, and its fifth lens groupmoved toward the object.

For focusing on an object at the near point, the fourth lens group ismoved toward the object. The duplet of the cemented lens pieces L13 andL14 are moved in directions normal to the optical axis so as to correctfuzziness of an image during photographing.

Optical data of the fourth embodiment of the zoom lens are provided inTable 10.

TABLE 10 NS R D Nd vd ΔPgF  1 426.3567 3.0000 1.83400 37.34  2 159.90660.0200 1.56732 42.84  3 159.9066 10.0500 1.49700 81.61 0.0375  4−684.4955 0.3000  5 140.0775 9.1000 1.49700 81.61 0.0375  6 8733.4134D(6)  7 558.1944 4.4000 1.80518 25.46  8 −61.1413 0.0100 1.56732 42.84 9 −61.1413 1.6000 1.72916 54.67 10 177.9802 2.6000 11 583.7869 1.50001.80450 39.64 12 50.6562 0.0100 1.56732 42.84 13 50.6562 3.4000 1.8051825.46 14 142.9473 3.7000 15 −73.8510 1.5000 1.90366 31.31 16 515.2175D(16) 17 432.7323 4.1000 1.49700 81.61 18 −112.9310 0.2000 19 73.57895.2184 1.48749 70.44 20 −95.0713 0.2000 21 87.0854 5.1506 1.48749 70.4422 −66.1655 0.0100 1.56732 42.84 23 −66.1655 1.5000 1.90366 31.31 24−710.1255 12.5500 25 −236.4657 0.9000 1.74400 44.79 26 27.5546 0.01001.56732 42.84 27 27.5546 4.1589 1.80610 33.27 28 99.2354 4.5500 29 STOP0.0000 D(29) 30 65.1174 4.1342 1.51742 52.15 31 −65.1174 0.2000 3250.5972 5.4000 1.51823 58.96 33 −48.1430 0.0100 1.56732 42.84 34−48.1430 1.3000 1.90366 31.31 35 1899.0359 0.0000 36 0.0000 D(36) 37113.8672 2.2800 1.83481 42.72 38 25.8597 6.9561 39 −55.4034 1.30001.48749 70.44 40 29.6386 0.0100 1.56732 42.84 41 29.6386 5.9000 1.7204734.71 42 −175.0744 D(42) 43 0.0000 2.0000 1.51680 64.20 44 0.0000 1.0000

Distances between the adjacent lens surfaces in several pairs in thefourth embodiment of the zoom lens are given in Table 11 below as wellas varied values of the focal distance f, the F-number Fno, and thefield angle ω for each of the photographing positions at the wide-angleposition (f=152.1633), at the intermediate zooming range (f=297.4851),and at the telephoto position (f=582.52), respectively.

TABLE 11 f 152.1633 297.4851 582.5200 Fno 4.99224 5.87742 6.53711 ω7.9436 4.07100 2.07820 D(6) 64.0000 111.2643 142.4400 D(16) 34.055123.2139 2.0400 D(29) 27.7980 17.1857 24.0639 D(36) 13.6386 8.2816 2.5000D(42) 51.0000 77.8106 97.8880

Distances between the adjacent lens surfaces in several pairs in thefourth embodiment of the zoom lens during focusing on an object at thenear point for photographing situation at the wide-angle position(f=152.1633), at the intermediate zooming range (f=297.4851), and at thetelephoto position (f=582.52), respectively, are given in Table 12 belowas well as varied values of the focal length f upon focusing on anobject at infinite distance away and the distance D(0) from the frontsurface of the first lens piece to the object.

TABLE 12 f 152.1633 297.4851 582.5200 D(0) 2399.28 2352.02 2320.84 D(29)26.1916 13.2535 12.8804 D(36) 15.2450 12.2138 13.6835

Embodiment 5

FIG. 17 is a vertical sectional view showing a lens arrangement of afifth embodiment of the zoom lens according to the present invention.The fifth embodiment of the zoom lens comprises the foremost or firstlens group G1 of positive refractive power located the closest to anobject, the succeeding second lens group G2 of negative refractivepower, the third lens group G3 of positive refractive power, the fourthlens group G4 of positive refractive power, and the fifth lens group G5of negative refractive power, all the lens groups being arranged in thisorder.

In the fifth embodiment of the zoom lens, the first lens group G1comprises a duplet of a meniscus lens piece L1 of negative refractivepower with its convex surface oriented to the object and a lens piece L2of positive refractive power cemented with the meniscus lens piece L1,and a meniscus lens piece L3 of positive refractive power with itsconvex surface oriented toward the object, all the lens pieces beingarranged in this order from the closest to the object in the foremostposition to the farthest from the object in the rearmost position.

The second lens group G2 comprises a duplet of a lens piece L4 ofpositive refractive power with its convex surface oriented toward theobject and a lens piece L5 of negative refractive power cemented withthe lens piece L4, another duplet of a meniscus lens piece L6 ofnegative refractive power with its convex surface oriented toward theobject and a lens piece L7 of positive refractive power cemented withthe lens piece L6, and a meniscus lens piece L8 of negative refractivepower with its concave surface oriented to the object.

The third lens group G3 comprises a biconvex lens piece L9, a biconvexlens piece L10, a duplet of a biconvex lens piece L11 and a lens pieceL12 of negative refractive power cemented with the lens piece L11, andanother duplet of a biconcave lens piece L13 and a meniscus lens pieceL14 of positive refractive power with its convex surface oriented to theobject, and cemented with the biconcave lens piece L13, all the lenspieces being arranged in this order from the closest to the object inthe foremost position to the farthest in the rearmost position.

The fourth lens group G4 comprises a biconvex lens piece L15, and aduplet of a biconvex lens piece L16 and a lens piece L17 of negativerefractive power cemented with the lens piece L16, all the lens piecesbeing arranged in this order from the closest to the object in theforemost position to the farthest from the object in the rearmostposition.

The fifth lens group G5 comprises a lens piece L18 of negativerefractive power with its convex surface oriented toward the object, anda duplet of a biconcave lens piece L19 and a biconvex lens piece L20cemented with the lens piece L19, all the lens pieces being arranged inthis order on the basis of the foremost first.

During shifting from the wide-angle position to the telephoto positionto vary magnification, the fifth embodiment of the zoom lens has itsfirst lens group moved toward the object, its second lens group held ina fixed position, its third lens group moved on a trajectory that drawsan arc toward the imaging plane relative to the second lens group, itsfourth lens group moved on a trajectory that draws an arc toward theimaging plane relative to the third lens group, and its fifth lens groupmoved toward the object.

For focusing on an object at the near point, the fourth lens group ismoved toward the object. The duplet of the cemented lens pieces L13 andL14 are moved in directions normal to the optical axis so as to correctfuzziness of an image during photographing.

Optical data of the fifth embodiment of the zoom lens are provided inTable 13.

TABLE 13 NS R D Nd vd ΔPgF  1 343.2915 3.0000 1.83400 37.34  2 145.90910.0200 1.56732 42.84  3 145.9091 10.0500 1.49700 81.61 0.0375  4−1465.0143 0.3000  5 146.8570 9.3000 1.49700 81.61 0.0375  6 −2192.2330D(6)  7 247.8836 4.5000 1.80518 25.46  8 −60.9978 0.0100 1.56732 42.84 9 −60.9978 1.6000 1.75243 49.57 10 122.8808 3.5590 11 −3272.8176 1.50001.83888 39.37 12 44.9185 0.0100 1.56732 42.84 13 44.9185 3.5140 1.8051825.46 14 172.9348 2.7259 15 −65.8855 1.5000 1.90366 31.31 16 −8818.9517D(16) 17 107.5605 4.2567 1.49700 81.61 18 −82.4101 0.2000 19 131.86123.5227 1.48749 70.44 20 −137.2545 0.2000 21 74.0878 5.3399 1.48749 70.4422 −69.9110 0.0100 1.56732 42.84 23 −69.9110 1.5000 1.90366 31.31 24−2310.5069 13.5458 25 −220.8383 1.2000 1.71680 45.46 26 29.9133 0.01001.56732 42.84 27 29.9133 4.1500 1.80610 33.27 28 95.4308 5.0000 29 STOP0.0000 D(29) 30 80.8865 4.1200 1.50860 59.40 31 −64.5149 0.2000 3237.7400 5.4200 1.50623 60.42 33 −57.0230 0.0100 1.56732 42.84 34−57.0230 1.3000 1.90366 31.31 35 797.3134 D(35) 36 94.7210 1.30001.82563 41.77 37 24.4742 6.4000 38 −55.8634 1.3000 1.48749 70.44 3925.9416 0.0100 1.56732 42.84 40 25.9416 5.6800 1.65673 32.70 41−226.3658 D(41) 42 0.0000 2.0000 1.51680 64.20 43 0.0000 1.0000

Distances between the adjacent lens surfaces in several pairs in thefifth embodiment of the zoom lens are given in Table 14 below as well asvaried values of the focal distance f, the F-number Fno, and the fieldangle ω for each of the photographing positions at the wide-angleposition (f=122.40), at the intermediate zooming range (f=304.04), andat the telephoto position (f=582.00), respectively.

TABLE 14 f 122.4004 304.0417 582.0046 Fno 4.5047 5.8152 6.5310 ω 10.0234.070 2.129 D(6) 46.8750 111.4683 141.3470 D(16) 36.4322 21.0752 2.0150D(29) 35.2507 19.3740 24.5725 D(35) 10.8554 6.7810 3.9750 D(41) 43.942779.2508 95.9185

Distances between the adjacent lens surfaces in several pairs in thefifth embodiment of the zoom lens during focusing on an object at thenear point for photographing situation at the wide-angle position(f=122.40), at the intermediate zooming range (f=304.04), and at thetelephoto position (f=582.00), respectively, are given in Table 15 belowas well as varied values of the focal length f upon focusing on anobject at infinite distance away and the distance D(0) from the frontsurface of the first lens piece to the object.

TABLE 15 f 122.40 304.04 582.52 D(0) 2217.380 2152.787 2122.908 D(29)34.11145 15.72925 14.53497 D(35) 11.99467 10.42577 14.01258

The values of the terms in the conditional expressions (1) to (4)regarding the first to fifth embodiments of the present invention aregiven in Table 16 below:

TABLE 16 Embodiment 1 2 3 4 5 βbt in the conditional 3.3442 3.71203.3690 3.3060 3.5770 expression (1) f1/√(fw · fT) in the 0.7965 0.83120.8788 0.8265 0.9242 conditional expression (2) ΔPgF in the conditional0.0375 0.0375 0.0375 0.0375 0.0375 expression (3) Lt/fT in theconditional 0.6207 0.6457 0.7213 0.6509 0.6479 expression (4)

We claim:
 1. A zoom lens having a telephoto end and a wide angle end,and comprising in order from the object side a first lens group having apositive refractive power, a second lens group having a negativerefractive power, a third lens group having a positive refractive power,a fourth lens group having a positive refractive power, and a fifth lensgroup, wherein the following conditional expression (2) is satisfied:0.7965≤f1/√{square root over ((fw×fT))}≤1.3  (2) where fw is a focallength of the zoom lens taking a wide-angle position, fT is a focallength of the zoom lens taking a telephoto position, and f1 is a focallength of the first lens group, wherein the first lens group comprisesat least one lens piece that satisfies the following conditionalexpression (3):0.018≤ΔPgF  (3) where PgF is the partial dispersion for glass for therespective wavelengths 435.8 nm, 486.1 nm, and 656.3 nm of spectrallines g, F, and C, given by the following expression (3):PgF=(ng−nF)/(nF−nC), where ng, nF, and nC are the refractive indices forthe respective wavelengths 435.8 nm, and 486.1 nm, and 656.3 nm ofspectral lines g, F, and C, and ΔPgF is a deviation from a straight linedefined by a first point having as its x, y coordinates the Abbeconstant on the d-line νd=60.49 and the partial dispersion PgF=0.5393for a glass type C7 and a second point having as its x, y coordinatesthe Abbe constant on the d-line νd=36.30 and the partial dispersionPgF=0.5829 for a glass type F2, where the Abbe constant on the d-line νdis given by the following expression:νd=(nd−1)/(nF−nC), where nd is the refractive index for the wavelength589.6 nm of spectral line d, wherein the following conditionalexpression (4) is satisfied:0.60≤Lt/fT≤0.75  (4) where Lt is an entire length of the optical systemof the zoom lens taking a telephoto position, and fT is a focal lengthof the same of the zoom lens at the telephoto position, wherein thesecond lens group is held in a fixed position while all the other lensgroups are displaced when zooming from a wide-angle position to atelephoto position to vary magnification, wherein a surface closest tothe object side of the third lens group is convex toward the objectside, wherein the third lens group is an immediately adjacent lens groupto the fourth lens group, and wherein during zooming from a wide-angleend to a telephoto end, the third lens group is axially moved toward theobject side.
 2. The zoom lens according to claim 1, wherein thefollowing conditional expression (1) is satisfied:3.1≤βbt≤4.0  (1) where βbt denotes a combined lateral magnification ofall lens groups at the telephoto end, rearward of the fourth lens group.3. The zoom lens according to claim 1, wherein the fifth lens group hasa negative refractive power.
 4. The zoom lens according to claim 1,wherein the zoom lens comprises an aperture stop closer to the imagingplane than the second lens group, and at least some of the lens groupscloser to the imaging plane than the aperture stop are displaceablealong the optical axis to shift a focal point from the point at infinityto an object at the near point.
 5. The zoom lens according to claim 1,wherein the zoom lens further comprises a sixth lens group closer to theimaging plane than the fifth lens group displaced toward the objectduring shifting from the wide-angle position to the telephoto positionto vary magnification.
 6. A camera device comprising: the zoom lensaccording to claim 1 and a solid-state image sensor disposed on orbehind the imaging plane of the zoom lens for converting an opticalimage created by the zoom lens into electrical signals.